The present invention relates to a magnetically driven pump, particularly in the form of a centrifugal pump of a single suction structure, in which a drive power of an electric motor is transmitted from a drive rotor to a follower rotor by way of a magnetic coupling, thus causing a rotating shaft with an impeller of the pump to turn integrally with the follower rotor.
In a centrifugal pump of a single suction structure of the above-mentioned type, an impeller is fixed to one end portion of the rotating shaft, which is rotatably supported in the center line of a pump casing by way of a supporting member attached internally to the casing. Furthermore, a bearing of ceramic material resistant to hard wear is interposed between the rotating shaft and the supporting member so as to withstand a high speed of rotation of the rotating shaft.
In the operation of the above-described centrifugal pump, a magnets-embedded drive rotor is rotated directly by an electric motor, and a magnets-embedded follower rotor opposed inside to the drive rotor is rotated accordingly by indirect way of a magnetic coupling, so that the rotating shaft with the impeller is caused to rotate integrally with the follower rotor. Due to the rotation of the rotating shaft, the impeller imparts centrifugal force to the liquid coming into a suction port which is configured in the axial center of the impeller, thus carrying the liquid radially in an accelerated manner.
However, the impeller sending out the liquid, at high speedy rotation, adversely receives an uneven reaction of axial load (thrust) and radial load, so that the rotating shaft is subjected to unbalanced vibration. For this reason, the ceramic bearing, which can withstand hard wear but is relatively low in toughness against breakage, suffers damage or breakage due to the influence of axial load and impact occurring with the vibration of the rotating shaft at high speedy rotation.
It is accordingly a primary object of the present invention to provide a magnetically driven pump, of which the ceramic bearing has no fear of damage and breakage, so designed as to relieve the influence of thrust load and vibration of the impeller rotating shaft at high speedy rotation on the ceramic bearing by absorbing such thrust load and vibration.
It is a secondary object of the present invention to provide a magnetically driven pump so designed as to prevent the likely vibration of the rotating shaft at high speedy rotation by the operation of a so-called self-aligning.
It is a further object of the present invention to provide a magnetically driven pump so designed as to save the likely wear and fatigue on the ceramic bearing due to contact with the rotating shaft by cooling the frictional heat which generates between the bearing and the rotating shaft.
With the above and other objects in view, the present invention provide a magnetically driven pump so designed that a drive power of an electric motor is transmitted from a magnets-embedded drive rotor to a magnets-embedded follower rotor opposed to one another by way of a magnetic coupling; comprising a pump casing separated internally by a partition into two rooms of which one accommodates the drive rotor and the other accommodates the follower rotor, a rotating shaft having a flange for determining the position of the follower rotor, and holding the follower rotor on one end portion thereof while holding an impeller on the other end, the rotating shaft being supported with an interposing bearing of ceramic material which is fitted into a supporting member fixed in the pump casing, a thrust bearing of ceramic bearing being juxtaposed in contact with said interposing bearing so as to receive an axial load of the rotating shaft, and a cushioning member being mounted on the rotating shaft in the position between the thrust bearing and said flange so as to push the thrust bearing from the rear.
Preferably, the interposing bearing has an exterior surface curved outwards like the bilge of a barrel, while an interior surface of the interposing bearing is provided with a spiral groove.